Diseases
Septoria helianthi Ell. et Kell. - Septoria Leaf Spot of Sunflower, Septoriosis.
Systematic position.
Class Deuteromycetes, order Sphaeropsidales, family Sphaerioidaceae, genus Septoria.Biological group.
Facultative parasite.Morphology and biology.
Septoria leaf spot of sunflower occurs on cotyledons at first. Then it spreads to the lower leaves and upper leaves in form of yellow, further dark brown, circular or irregular-shaped spots (necroses). The spots have light border on the upper side of a leaf and light-gray one on its lower side. The spots are visible between veins on the whole surface of leaves, but being more numerous at their apex. Pycnidia to 150 microns in diameter are formed mainly on upper side of necrosis, producing hyaline, direct or slightly bent, pointed, 1-5-septate conidia. Their size varies in the limits 35-70 x 2.2-6.7 microns. The necrotic tissue drops out gradually, therefore leaves become perforated. The disease may be sometimes found on stalks and heads. The main source of the infection is the infected sunflower residues, and the secondary source is the seeds. The Septoria Leaf Spot of Sunflower is insufficiently studied in Russia and other countries of the former USSR.Distribution.
Septoria Leaf Spot of Sunflower is spread in Russia and other countries of the former USSR everywhere.Ecology.
Disease intensively accrues after flowering of sunflower. Optimum conditions for its development are air temperature 22-25oC and abundant rainfall.Economic significance.
Sunflower withers early at high severity of the disease. Sometimes it causes appreciable loss of yield as it took place in former Yugoslavia and other countries. Septoria has yet no economic significance in Russia and other countries of the former USSR. Control measures against the Septoria Leaf Spot of Sunflower are optimal crop rotation, the use of resistant varieties and hybrids, presowing seed dressing.Related references:
Gorlenko, M.V. 1968. Diseases of sunflower. In: Gorlenko, M.V. Agricultural phytopathology. Moscow: Vysshaya shkola, p. 196-208 (in Russian).Kukin, V.F. 1982. Diseases of sunflower and control measures against theirs. Moscow: Kolos, 80 p. (in Russian).
Maric A., Camprag D., & Masirevic S. 1987. Sunflower diseases and pests and their control. Belgrade: Nolit, 379 p. (in Serbian).
Tikhonov, O.I. 1975. Diseases of sunflower. In: Pustovoit, V.S., ed. Sunflower. Moscow: Kolos, p. 401-409 (in Russian).